This invention relates generally to pen-based computing systems, and more particularly to attenuating friction noise or click noise captured by an audio recording device embedded in a smart pen.
As audio recording device size has decreased while recording quality has increased, use of audio recording devices as standalone devices or as components of other devices has become more common. For example, it has become common to include audio recording devices in writing devices, such as including an embedded audio recording device in a digital pen or “smart pen.” This embedded audio recording device allows the smart pen to be used for both writing and recording audio while writing.
However, noise caused by writing with the smart pen often compromises the quality of audio captured by the embedded audio recording device. One primary source of noise while writing, or “writing noise,” is “friction noise” which is produced as the tip of the smart pen moves across a writing surface. Another source of writing noise is “click noise” which occurs when the tip of the smart pen contacts the writing surface or is lifted from the writing surface. Typical implementations of smart pens allow these types of writing noises to be captured loudly enough to distort other audio data.
Generally, smart pens employ a switch mechanism using a graphite or ink writing cartridge to activate a force sensing resistor (“FSR”), or other sensor such as a strain gauge, piezoelectric force sensor, or optical sensor detecting contact between writing surface and smart pen tip, to notify the smart pen system that the tip of the smart pen has contacted a writing surface or has been removed from contacting a writing surface. To allow the writing cartridge to freely move in and out of the smart pen and activate or deactivate the FSR, smart pens are commonly designed so that the interior bore diameter of the smart pen is sufficiently larger than the writing cartridge's external diameter. This design reduces the likelihood that the writing cartridge will become stuck in the smart pen's internal cavity or that the smart pen will cause friction preventing proper activation of the FSR and accurate capture and digitization of the writing.
However, designing the internal cavity diameter of the smart pen to be sufficiently larger than the external bore diameter of the writing cartridge allows the writing cartridge to contact the internal cavity of the smart pen when the writing cartridge contacts a writing surface. The size difference between the smart pen internal diameter and the writing cartridge external diameter also allows the cartridge to contact the internal cavity of the smart pen when the smart pen tip is lifted from the writing surface. Additionally, friction and/or click noise caused by writing with the smart pen can be captured by the embedded audio recording device externally through the air (“aurally”) or internally through component coupling and/or internal air cavities inside the pen (“mechanically”).
Accordingly, there is a need for a system and method to remove or attenuate the friction and/or click noise captured by an embedded audio recording device during writing with a smart pen.